Stem cells are cells with the potential to develop into many different types of cells in the body. They serve as a repair system for the body. There are two main types of stem cells: embryonic stem cells and adult stem cells. Doctors and scientists are excited about stem cells because they have potential in many different areas of health and medical research. Studying stem cells may help explain how serious conditions such as birth defects and cancer come about. Stem cells may one day be used to make cells and tissues for therapy of many diseases, including Parkinson's disease, Alzheimer's disease, spinal cord injury, heart disease, diabetes and arthritis.

Stem cells are unprogrammed cells in the human body that can be described as "shape shifters." These cells have the ability to change into other types of cells. Stem cells are at the center of a new field of science called regenerative medicine. Because stem cells can become bone, muscle, cartilage and other specialized types of cells, they have the potential to treat many diseases, including Parkinson's, Alzheimer's, diabetes and cancer. Eventually, they may also be used to regenerate organs, reducing the need for organ transplants and related surgeries. "Stem cells are like little kids who, when they grow up, can enter a variety of professions," Dr. Marc Hedrick of the UCLA School of Medicine says. "A child might become a fireman, a doctor or a plumber, depending on the influences in their life -- or environment. In the same way, these stem cells can become many tissues by making certain changes in their environment."